Terminal structure for wiring devices

ABSTRACT

This invention relates to an improved push-in type terminal construction for wiring devices using a resilient beam constrained at one end and freely supported at the other instead of the conventional cantilever. A greater clamping force and simplified construction is provided and the terminal is mountable in a wiring device so as to be visible.

United States Patent Huibrechtse 3,638,171 51 Jan. 25, 19 72 Limited, Toronto, Ontario, Canada Apr. 25, 1969 [2]] Appl. No.: 819,209

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Primary Examiner-Ian A. Calvert [22] Filed:

Attorney-Paul E. Rochiord, Frank L. Neuhauser and Oscar B. Waddell l. a .mm m Nb 3 n.m hs mm a 8 T v .m C 0 A W R m a m w H m 0 8 .m w. hw mr m in mm WC .mm .1 m 7 i o Kw TC 2 5 2%9 l 5 w 2 W 3 D 3 9 wm M l m aw u" w m m 3 m m u m m2 m4 m6 1 m m3 m u .l. "I n. n9 3 muh m "m "mam L m I o d s xm UIlF 1]] 2 8 555 [.ll.

Reerences Cited strained at one end and freely supported at the other instead of the conventional cantilever. A greater clamping force and simplified construction is provided and the terminal is mountable in a wiring device so as to be visible.

UNITED STATES PATENTS Pacent...........................339/95 D UX 1,950,826 3/1934 Smart ....339/262 7 Clalms, 4 Drawing Figures TERMINAL STRUCTURE FOR WIRING DEVICES This invention relates in general to wire connecting or terminal structures for electric wiring devices.

More specifically the invention comprises an improvement in terminal structures which more closely proximates the desirable characteristics of the well known screw-connector expedient while avoiding the problems and deficiencies inherent in the use of the latter.

As is well known, when employing a screw head for connecting a wire lead to a contact member, .the wire, in addition to stripping, must be appropriately looped. While sufi'rcient torque must be applied to obtain a satisfactory clamping action, care must be exercised to avoid stripping the threads of the screw or the tapped hole in the contact. However, unless sufi'rcient pressure is applied, good electrical and thermal connection cannot be guaranteed.

In short, a successful application of the screw expedient depends upon human efiiciency and the exercise of care, factors which demand the expenditure of considerable time.

In an effort to provide consistently good connections while minimizing hookup time, the art introduced what may be termed the push-in type innovation. In one basic form, this innovation utilizes an apertured cantilevered spring member mounted adjacent to, or connected to, a contact bar located in a wiring device. A lead wire is introduced through the aperture of the spring member and is biased into engagement with the contact bar. The lead is restrained from withdrawal by the frictional force exerted on it by a sharp edge of the spring aperture. There are many known variations of the push-in type innovation most using the same basic concept and relying on cantilever springs for clamping.

While the push-in type units have proven to be most acceptable insofar as simplicity of connection is concerned, many prior efforts to increase clamping pressure and efficiency have led to relatively expensive structures. For this reason and other factors well known to the art, although the push-in type devices have been commercially successful, lower cost higher performance devices of the push-in mode of operation are highly desirable.

Possibly the prime objective is to obtain sufficient contact pressure without resort to expensive, sophisticated improvements of the retaining spring which not only increase manufacturing costs but render use by those not skilled in the art more difficult and unobvious.

In view of the wide commercial interest in improved push-in type connectors and certain problems regarding the prior art in this area, it is the main object of the present invention to provide an improved and extremely simple push-in type terminal structure for use in wiring devices.

A further object of the invention is to provide a terminal structure which is simple to manufacture and use but which affords substantially the same connection characteristic as a correctly effected screw connector.

A still further object of the invention is to provide a terminal structure which is readily mounted on, or in, a wiring device such that the actual connection can be observed as it is made and can subsequently be visually inspected when desired.

A further object of the invention is to provide a terminal structure of the push-in type which can be used to modify existing devices, replacing screw terminal means.

Further objects and advantages will become apparent from the following detailed description taken in conjunction with the appended drawings wherein:

FIG. 1 is a perspective view of an electric wiring device embodying the invention;

FIG. 2 is a partial cross section of a wiring device showing a preferred terminal structure;

FIG. 3 is a view similar to FIG. 2 with a wire lead inserted in the terminal structure, and

FIG. 4 is a partial view of a terminal structure in elevation.

It will be appreciated by those skilled in the art that the novel concept herein disclosed finds application in many diverse forms of wiring device. Thus, while an electric outlet has been selected for purposes of illustration and description of the invention, the full scope of the latter should only be construed with reference to the appended claims.

Initially, with reference to FIG. I, an electric outlet assembly 10 is shown to include a pair of conventional connector sockets l2 and, at each side, mounted in apertures 14 formed in the outlet casing, terminal structures 16 are located.

As will be noted, the base 18 of the outlet assembly includes a plurality of holes 20 through which stripped wire leads can be inserted for engagement with the terminal structures.

Turning to FIGS. 2 and 3, a preferred embodiment of the invention is shown in schematic representation. In this embodiment the terminal structure comprises a contact bar 22 mounted in the outlet assembly adjacent an aperture 14. The front edgeof contact bar 22 is located in a recess 24 formed in the main casing portion 26, while the rear edge of contact bar 22 is mounted in insulated abutment with the base 18.

While FIG. 1 illustrates a double contact or terminal structure on the side of the outlet, only one terminal will be described in the interests of clarity and simplicity. All terminals in the illustrative embodiment are identical with one another.

The clamping, retaining or connecting member shown consists of a resilient, apertured beam member 28 which can be manufactured from stainless steel strip or any spring stock which will retain its resilience under all conditions to which its associated wiring device may be exposed.

With further reference to FIGS. 2 and 3 it will be seen that one end of beam member 28 is substantially locked or secured in the aforementioned recess 24 by frictional engagement with the front edge of contact bar 22 and an inner face of recess 24.

The other end of beam member 28 is housed in a recess 30 formed in base 18 adjacent the wire entry hole 20. When deflected by insertion of a wire, as shown in FIG. 3, the beam member is freely supported by the inner wall of recess 30. Thus, in its operative condition, the clamping means, (i.e., the beam member 28), is, in fact, a beam, constrained or fixedly supported at one end, and freely supported at the other. Reference to the basic statics of such a beam reveals that the clamping means of the present invention will exert approximately 35 times the clamping force of an identical beam, mounted as a cantilever and subjected to an identical deflection. In short, the terminal structure closely approaches the clamping ability of the screw-type connector.

It will be readily appreciated that satisfactory results could be obtained even if the beam member was freely supported at both ends or fixedly supported at both ends, Changes of this nature would depend to a large extent on the wiring device involved and any peculiarities regarding its overall structure.

The aperture 34 of beam member 28 is, of course, wide enough to accept preselected gauges of wire, such gauges depending on the current-carrying capacity required.

In the illustrated embodiment the length of aperture 34 is governed by the provision and location of a stop member 36 and a pair of laterally spaced guide members 38, the last mentioned members and stop member 36 being formed in contact bar 22 as by dimpling, upsetting or the like.

Stop member 36 is located towards the front edge of contact bar 22 and below aperture 34. It is provided to govern the extent of wire insertion and is located as noted above so that it in no way affects beam member 28.

In contradistinction, guide members 38 are formed or provided rearwardly of the clamping edge 40, (see FIG. 3), in order to maintain the beam member deflected upwardly away from the contact bar. Guide members 38 also serve to restrain an inserted wire against lateral movement such that, in combination with stop member 36 and beam member 28, these elements assist in maintaining an inserted lead wire in substantially stationary contact with the contact bar 22. This further illustrates the functional proximity of the present invention to the screw expedient.

To efi'ect connection of a lead wire with a terminal structure of the present invention, it is only necessary to strip in appropriate length, insert the stripped wire through wire hole 20 and push until the end of the wire abuts stop member 36. At this point the beam member 28 has been deflected as shown in FIG. 3 and the relatively sharp edge 40 of aperture 34 tends to bite into the lead to prevent inadvertent withdrawal thereof while applying the clamping force necessary to obtain the requisite contact between the lead and the contact bar.

To release the connection, the beam member is merely raised slightly by inserting a screwdriver tip or the like. This is readily accomplished due to the fact that the terminal structure is very accessible, lying as it does on the outer surface of the wiring device. It will also be noted that, unlike prior art counterparts, the base 18 includes no releas" holes such that there can be no confusion or error in selecting correct wire insertion holes.

From the foregoing, many changes and modifications will become apparent to those skilled in the art without departing from the spirit and scope of the invention. As a result of this, and as noted before, the scope of the invention is set forth in the claims attached hereto.

I claim:

1. A terminal structure for a wiring device comprising insulating housing means and conductive electric contact means mounted in said housing, retaining slots in said housing, wireretaining means having a fixed end wedged in one of said slots proximate said electric contact means,

and a free end spaced from said electric contact and supported in another of said slots,

said wire-retaining means comprising a resilient apertured metal beam member, and the midportion of said wire retaining means being positioned by location of said slots in said device in predetermined spaced adjacency to said contact means, and in a plane at an acute angle relative thereto,

a wireentry hole aligned parallel to a surface of said electric contact means against which the fixed end of said wireretaining means is wedged,

the free end of said wire-retaining means being closest to the wire entry hole and being spaced from the electric contact means by a distance greater than the diameter of the wire entry hole.

2. A terminal structure for a wiring device comprising,

insulating housing means and conductive electric contact means mounted in said housing,

wire-retaining means proximate said electric contact,

retaining slots in said housing,

said wire-retaining means comprising a resilient apertured metal beam member,

both ends thereof being supported in said terminal slots,

and the midportion of said wire-retaining means being positioned by location of said slots in said device in predetermined spaced adjacency to said contact means,

and in a plane at an acute angle thereto,

said electric contact having stop means located adjacent a front edge thereof and guide means located proximate a rear edge thereof.

3. A terminal structure for a wiring device as claimed in claim 2 wherein said stop means comprises'a protuberance formed on said contact means operable to limit insertion of a wire lead and wherein said guide means comprises a pair of detents laterally spaced about the longitudinal axis of the beam member and located on the contact means to hold said other end of the beam member in spaced relationship to the conta'ct means.

4. A wiring device including, in combination,

a casing;

at least one terminal aperture defined in a sidewall of said casing;

a wire entry hole defined in a backwall of said casing, 1

retaining slots in said housing,

contact means mounted in said casing adjacent said terminal aperture and having a surface aligned in parallel with said wire entry hole, wire retaining means separate from said contact means mounted exteriorly of the contact means and operable to retain an inserted wire in clamped relationship with the contact means,

said wire-retaining means including at least one resilient, apertured beam member fixedly supported at one end thereof in one of said retaining slots on one edge of said contact means and freely supported at the other end in a second retaining slot spaced from said electric contact means by a distance greater than the diameter of the wire entry hole,

said beam member extending in and across the path of travel of a wire entering through said wire entry hole and said beam member being in a plane lying at an acute angle relative to the plane of said contact means.

5. A wiring device including, in combination,

a casing,

said casing having at least one terminal aperture formed in a sidewall thereof;

and said casing having a wire entry hole formed in a rear wall thereof,

a contact bar mounted in said casing adjacent said terminal aperture, and having a surface aligned parallel with said contact bar said contact bar having a first edge and a second edge;

at least one resilient, apertured beam member separate from said contact bar mounted within the periphery of the terminal aperture and lying in a plane at an acute angle relative to the plane of the contact bar, with the edge thereof closest to the wire entry hole spaced the greatest distance from the contact bar, the end of the beam member more remote from said wire entry hole being fixedly supported on said first edge of the contact bar and the other end of said beam member being afforded free support by said casing adjacent and spaced from said second edge of said contact bar at a distance greater than the diameter of the wire entry hole such that, on inserting a wire between the contact bar and the beam member, the wire is retained in clamped relationship with said contact bar.

6. A wiring device as claimed in claim 5 and further including a pair of spaced detents located on the contact bar along a line transverse to the longitudinal axis of the beam member, said detents being operable to engage the beam member in its inoperative condition to maintain same in its said predetermined plane and to hold the said other end of the beam member substantially out of immediate contact with the easing.

7. A wiring device as claimed in claim 5 and further including a stop member located on said contact bar at the portion of said bar proximate the end of the aperture nearest the fixed end of said beam member, said stop member being operable to limit the insertion of a wire between the contact bar and the beam member.

s a s s s 

1. A terminal structure for a wiring device comprising insulating housing means and conductive electric contact means mounted in said housing, retaining slots in said housing, wireretaining means having a fixed end wedged in one of said slots proximate said electric contact means, and a free end spaced from said electric contact and supported in another of said slots, said wire-retaining means comprising a resilient apertured metal beam member, and the midportion of said wire retaining means being positioned by location of said slots in said device in predetermined spaced adjacency to said contact means, and in a plane at an acute angle relative thereto, a wire entry hole aligned parallel to a surface of said electric contact means against which the fixed end of said wireretaining means is wedged, the free end of said wire-retaining means being closest to the wire entry hole and being spaced from the electric contact means by a distance greater than the diameter of the wire entry hole.
 2. A terminal structure for a wiring device comprising, insulating housing means and conductive electric contact means mounted in said housing, wire-retaining means proximate said electric contact, retaining slots in said housing, said wire-retaining means comprising a resilient aperturEd metal beam member, both ends thereof being supported in said terminal slots, and the midportion of said wire-retaining means being positioned by location of said slots in said device in predetermined spaced adjacency to said contact means, and in a plane at an acute angle thereto, said electric contact having stop means located adjacent a front edge thereof and guide means located proximate a rear edge thereof.
 3. A terminal structure for a wiring device as claimed in claim 2 wherein said stop means comprises a protuberance formed on said contact means operable to limit insertion of a wire lead and wherein said guide means comprises a pair of detents laterally spaced about the longitudinal axis of the beam member and located on the contact means to hold said other end of the beam member in spaced relationship to the contact means.
 4. A wiring device including, in combination, a casing; at least one terminal aperture defined in a sidewall of said casing; a wire entry hole defined in a backwall of said casing, retaining slots in said housing, contact means mounted in said casing adjacent said terminal aperture and having a surface aligned in parallel with said wire entry hole, wire retaining means separate from said contact means mounted exteriorly of the contact means and operable to retain an inserted wire in clamped relationship with the contact means, said wire-retaining means including at least one resilient, apertured beam member fixedly supported at one end thereof in one of said retaining slots on one edge of said contact means and freely supported at the other end in a second retaining slot spaced from said electric contact means by a distance greater than the diameter of the wire entry hole, said beam member extending in and across the path of travel of a wire entering through said wire entry hole and said beam member being in a plane lying at an acute angle relative to the plane of said contact means.
 5. A wiring device including, in combination, a casing, said casing having at least one terminal aperture formed in a sidewall thereof; and said casing having a wire entry hole formed in a rear wall thereof, a contact bar mounted in said casing adjacent said terminal aperture, and having a surface aligned parallel with said contact bar said contact bar having a first edge and a second edge; at least one resilient, apertured beam member separate from said contact bar mounted within the periphery of the terminal aperture and lying in a plane at an acute angle relative to the plane of the contact bar, with the edge thereof closest to the wire entry hole spaced the greatest distance from the contact bar, the end of the beam member more remote from said wire entry hole being fixedly supported on said first edge of the contact bar and the other end of said beam member being afforded free support by said casing adjacent and spaced from said second edge of said contact bar at a distance greater than the diameter of the wire entry hole such that, on inserting a wire between the contact bar and the beam member, the wire is retained in clamped relationship with said contact bar.
 6. A wiring device as claimed in claim 5 and further including a pair of spaced detents located on the contact bar along a line transverse to the longitudinal axis of the beam member, said detents being operable to engage the beam member in its inoperative condition to maintain same in its said predetermined plane and to hold the said other end of the beam member substantially out of immediate contact with the casing.
 7. A wiring device as claimed in claim 5 and further including a stop member located on said contact bar at the portion of said bar proximate the end of the aperture nearest the fixed end of said beam member, said stop member being operable to limit the insertion of a wire between the contact bar and the beam member. 